JP2003322547A - Rotational position detecting device in bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotational position detecting device integrated into a bearing, having a simple constitution, being high in resolution, and allowing absolute detection. <P>SOLUTION: This bearing 10 is formed by arranging a plurality of balls 11 held at a prescribed interval by a retainer between an inner race 12 and an outer race 13, and is provided with a stator part 1 for arranging a plurality of AC exciting magnetic poles A to D at a prescribed interval along the circumference formed by a rolling locus of the balls held by the retainer so as to be fixed to the outer race 13. A position of the balls 11 to the respective AC exciting magnetic poles A to D changes accompanying that the balls 11 composed of a magnetic responsive construction material such as a steel ball roll along the circumference together with the retainer, and takes out an output signal for indicating an impedance change according to this position change by coils L1 to L4 arranged on the respective AC exciting magnetic poles A to D. A magnetic responsive cam part may be arranged in the inner race 12. The magnetic responsive cam part may be arranged in the retainer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational position detecting device for a rolling type bearing, in other words, to a bearing integrally provided with a rotational position detecting function.

[0002]

2. Description of the Related Art In a rotary shaft to which a bearing is applied, a position detecting device is often applied for detecting and controlling a rotational position. In such a case, if the position detection device is built into the bearing itself instead of mounting the rotation position detection device separately from the bearing, it is convenient and convenient, and also leads to cost reduction. . Conventionally known bearings equipped with this type of rotational position detecting device include a combination of a permanent magnet and a magnetoresistive element. However, in that case, it has only a detection function as an incremental pulse generator and the detection resolution is poor. It is also expensive.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a rotational position detecting device having a simple structure suitable for being integrally arranged in a rolling bearing. In addition, it is an object of the present invention to provide a rotational position detection device which has a simple configuration but is also excellent in detection resolution as compared with the incremental pulse generation method.

[0004]

A rotary position detecting apparatus according to a first aspect of the present invention is a rolling type in which a plurality of rolling elements held by a retainer at predetermined intervals are arranged between an inner ring and an outer ring. In the bearing of 1, the stator section is provided with a plurality of alternating-current excitation magnetic poles arranged at predetermined intervals along the circumference formed by the rolling locus of the rolling element held by the retainer,
The rolling element is made of a magnetically responsive material, and as the rolling element rolls along the circumference along with the retainer, the position of the rolling element with respect to each of the AC excitation magnetic poles changes, and depending on this position change, It is characterized in that an output signal indicating the impedance change is taken out by a coil arranged on the AC excitation magnetic pole.

When the inner ring is fixed to the bearing target shaft and the outer ring is fixed to a stationary body such as a frame of a machine, the inner ring rotates as the target shaft rotates, and the outer ring always remains stationary. At that time, the rolling elements (for example, balls) held by the retainer are
Together with the retainer, the inner ring is decelerated in the direction opposite to the direction of rotation of the inner ring to rotate. This reduction ratio is appropriately determined by the bearing design. In this way, the rotational positions of the retainer and the rolling element show a predetermined correlation with the rotational position of the target shaft fixed to the inner ring, so the rotational position of the target shaft can be detected by detecting the rotational position of the retainer and the rolling element. Can be detected. According to the first aspect, since the displacement of the rolling element of the bearing is detected, the configuration is simple and the manufacturing cost is low. Further, since the rotational position is detected based on the output signal indicating the impedance change corresponding to the position change of the rolling element, the absolute position can be detected with high detection resolution.

A rotational position detecting device according to a second aspect of the present invention is a rolling type bearing in which a plurality of rolling elements held by a retainer at predetermined intervals are arranged between an inner ring and an outer ring. A stator part formed by arranging a plurality of alternating-current excitation magnetic poles at a predetermined interval along the circumference formed by the rolling locus of the rolling element held by the above-mentioned rolling element, wherein the plurality of rolling elements are made of a magnetically responsive material. A first group and a second group made of a material that does not respond to magnetism, and the rolling element rolls along the circumference along with the retainer, so It is characterized in that the positions of the first and second groups change, and an output signal showing an impedance change corresponding to the position change is taken out by a coil arranged in the AC excitation magnetic pole. Also in this case, since the displacement of the rolling element of the bearing is detected, the structure is simple and the manufacturing cost is low. Further, since the rotational position is detected based on the output signal indicating the impedance change corresponding to the position change of the rolling element, the absolute position can be detected with high detection resolution.

A rotational position detecting device according to a third aspect of the present invention is a bearing having a plurality of rolling elements arranged between an inner ring and an outer ring, the bearing being fixed to one of the outer ring and the inner ring. A stator part having a plurality of alternating magnetic poles arranged at predetermined intervals along the circumference, and a magnetic responsiveness having a cam shape which is fixed to the other of the outer ring or the inner ring and shows a deviation with respect to the circumference. A cam portion, the position of the magnetically responsive cam portion with respect to each of the AC excitation magnetic poles changes with the relative rotation of the inner ring with respect to the outer ring, and an output signal indicating an impedance change corresponding to this position change is output as the AC signal. It is characterized in that it is taken out by a coil arranged on the exciting magnetic pole. Thus, by detecting the relative rotational position of the outer ring and the inner ring by the combination of the stator section and the magnetically responsive cam section provided on the outer ring and the inner ring, respectively, the rotational position of the target shaft to be bearing can be detected. You can Also in this case, the structure is simple and the manufacturing cost is low. Further, since the rotational position is detected based on the output signal indicating the impedance change corresponding to the position change, the absolute position can be detected with high detection resolution.

A rotational position detecting device according to a fourth aspect of the present invention is a rolling type bearing in which a plurality of rolling elements held by a retainer are arranged between an inner ring and an outer ring. Is provided with a stator portion in which a plurality of alternating-current excitation magnetic poles are arranged at a predetermined interval along the circumference of the retainer, and the retainer has a cam-shaped magnetic responsiveness showing a deviation with respect to the circumference of the movement trajectory. The cam part is formed,
As the retainer moves along the circumference, the position of the magnetically responsive cam portion with respect to each of the AC exciting magnetic poles changes, and an output signal indicating an impedance change corresponding to this change in position is distributed to the AC exciting magnetic poles. It is characterized in that it is taken out by the coil. As a result, the rotation of the magnetically responsive cam portion provided on the retainer is detected by the stator portion, and the rotational position of the bearing target shaft can be detected accordingly. Also in this case, the structure is simple and the manufacturing cost is low. Further, since the rotational position is detected based on the output signal indicating the impedance change corresponding to the position change, the absolute position can be detected with high detection resolution.

A rotational position detecting device according to a fifth aspect of the present invention is a rolling type bearing in which a plurality of rolling elements held by a retainer are arranged between an inner ring and an outer ring. The first stator part is fixed to one side and has a plurality of alternating-current excitation magnetic poles arranged at a predetermined interval along the circumference thereof, and is fixed to the other of the outer ring or the inner ring, and with respect to the circumference thereof. The first cam shape that shows the bias
A first detection unit including a magnetically responsive cam unit,
With the relative rotation of the inner ring with respect to the outer ring, the position of the first magnetically responsive cam portion with respect to each AC excitation magnetic pole of the first stator portion changes, and an output signal indicating an impedance change corresponding to the position change is output. The second stator part, which is taken out by a coil disposed on the AC exciting magnetic pole of the first stator part, and on the other hand, has a plurality of AC exciting magnetic poles arranged at predetermined intervals along the circumference formed by the moving path of the retainer, and the retainer. A second magnetically responsive cam portion disposed in the second
A detector is further provided, and as the retainer moves along the circumference, the position of the second magnetically responsive cam part with respect to each AC excitation magnetic pole of the second stator part changes, and this position change It is characterized in that an output signal showing a corresponding impedance change is taken out by a coil arranged in the AC exciting magnetic pole of the second stator section. This is a combination of the first detector according to the third aspect and the second detector according to the fourth aspect. This also provides the same operation and effect as described above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention, in which (a) is a schematic axial sectional view,
(B) is a schematic front view. In FIG. 1, the bearing 10 is
A plurality of (seven in the illustrated example) balls (rolling elements) 11 held by a retainer (not shown) at predetermined intervals are provided with an inner ring (inner race) 12 and an outer ring (outer race) 13.
It consists of a rolling type bearing that is placed between and. Although illustration of the retainer is omitted for convenience, as the retainer itself, one used in an existing bearing (ball bearing) may be appropriately used. In the illustrated example, the bearing target shaft 50 is coupled to the inner ring 12, and the inner ring 12 rotates as the shaft 50 rotates. The outer ring 13 is fixed to a machine frame or the like and stands still.

The stator 1 of the position detector is fixed to the outer ring 13 and stands still. In this stator portion 1, a plurality of AC excitation magnetic poles A, B, C, D are arranged at predetermined intervals along the circumference formed by the rolling locus of the balls 11 held by the retainer (that is, the rotation locus of the retainer). Become. In this example,
Each of the AC excitation magnetic poles A, B, C, D has a magnetic core 1a, 1
b, 1c, 1d, and a coil L wound around the magnetic core
1, L2, L3, L4, and each coil L1 to L
4 is excited by a predetermined AC signal (for example sinωt). The ball (rolling element) 11 built in the bearing 10 is made of a commonly known steel ball, and is made of a magnetic material, that is, a magnetically responsive material. As the ball 11 rolls along the circumference with the retainer, the position of the ball 11 with respect to each of the AC excitation magnetic poles A to D of the stator portion 1 changes, and an output signal indicating an impedance change corresponding to this position change is generated. It can be taken out by the coils L1 to L4 arranged on the AC excitation magnetic poles A to D.

AC exciting magnetic poles A to D in the stator section 1
1B, as shown in FIG. 1B, each pole A has a corresponding relationship with the ball 11 that is displaced according to the rotation of the target shaft 50.
It is set so as to show different mechanical phases between .about.D. For example, the impedance change of the pole A with respect to the displacement of the ball 11 (which is referred to as “θ” for convenience) is set so as to show the sine function characteristic sin θ, and the impedance change of the pole B is set so as to show the cosine function characteristic cos θ. , And the impedance change of the pole C is set so as to show the minus sine function characteristic −sin θ, and the impedance change of the pole D is set so as to show the minus cosine function characteristic −cos θ. Therefore, the ball 1 held by the retainer
The arrangement of the AC excitation magnetic poles A to D is determined so that the impedance characteristics of the AC excitation magnetic poles A to D of the stator portion 1 exhibit predetermined characteristics according to the number of 1s, that is, the intervals between the plurality of balls 11. . In this case, the mechanical displacement indicating the phase change θ of the impedance change of each pole A to D in one cycle of 0 to 360 degrees corresponds to the interval between the adjacent balls 11. For example, as shown in the figure, the bearing 10 has seven balls 11
, The distance between adjacent balls 11 is 360 degrees equal to 7
The mechanical displacement corresponding to the divided mechanical angle and showing the change in one cycle in which the phase angle θ of the impedance change of each pole A to D is 0 degree to 360 degrees corresponds to “360 degrees / 7”. In addition,
The rotation of the retainer, that is, the rolling of the ball 11 with respect to the rotation of the target shaft 50 is decelerated in the opposite direction. Therefore, θ
Does not directly indicate the rotation angle of the target shaft 50, but corresponds to the rotation position of the target shaft 50 in a predetermined relationship. By measuring θ, the rotation position of the target shaft 50 is detected. can do.

Here, the impedance change A (θ) of the ideal sine function characteristic that occurs in the coil L1 can be equivalently expressed by an expression such as A (θ) = P ₀ + Psin θ. Since the impedance change does not enter the negative region, the offset value P ₀ is larger than the amplitude coefficient P (P ₀ ≧ P) in the above equation, and “P ₀ + Psin”.
“θ” does not have a negative value. On the other hand, the coil L3 showing a differential characteristic with respect to the impedance change of the coil L1.
The impedance change C (θ) of the ideal negative sine function characteristic that occurs in C can be equivalently expressed by an equation such as C (θ) = P ₀ −Psin θ. On the other hand, the impedance change B of the ideal cosine function characteristic generated in the coil L2
(Θ) can be equivalently expressed by an expression such as B (θ) = P ₀ + Pcos θ. Further, the coil L4 showing a differential change with respect to the impedance change of the coil L2.
The impedance change D (θ) of the ideal negative cosine function characteristic that occurs in 1 can be equivalently expressed by an equation such as D (θ) = P ₀ −Pcos θ. It should be noted that since there is no inconvenience in the description even if P is regarded as 1 and omitted, it will be omitted in the following description.

FIG. 2 shows an example of an electric circuit applicable to the rotational position detecting device shown in FIG. Note that this circuit configuration is not limited to the bearing rotational position detecting device having the structure of the first embodiment shown in FIG. 1, but any of the rotational position detecting devices of the present invention having structures according to other embodiments. It is also applicable in. In FIG. 2, the coils L1 to L4 are equivalently shown as variable inductance elements. Each coil L
1 to L4 are subjected to constant voltage excitation in one phase by a predetermined AC signal (for convenience, this is indicated by Esinωt) given from the AC source 30. Voltage V generated in each coil L1 to L4
a, Vb, Vc, and Vd are the coils L corresponding to the angle variable θ corresponding to the rotational position to be detected, as described below.
The magnitude according to the impedance value for each of 1 to L4 is shown. _{Va = (P 0 + sinθ)} sinωt Vb = (P 0 + cosθ) sinωt Vc = (P 0 -sinθ) sinωt Vd = (P 0 -cosθ) sinωt

The calculator 31 obtains the difference between the output voltage Va of the coil L1 of the stator pole A and the output voltage Vc of the coil L3 of the stator pole C which changes differentially with respect to the output voltage Va, as described below, and determines the angle variable. An AC output signal having an amplitude coefficient having a sine function characteristic of θ is generated. Va−Vc = (P ₀ + sin θ) sin ωt− (P ₀ −s
in θ) sin ωt = 2 sin θ sin ωt The calculator 32 calculates the coil L of the stator pole B as follows.
The difference between the output voltage Vb of 2 and the output voltage Vd of the coil L4 of the stator pole D, which changes differentially, is obtained, and an AC output signal having an amplitude coefficient of the cosine function characteristic of the angle variable θ is generated. Vb−Vd = (P ₀ + cos θ) sin ωt− (P ₀ −c
osθ) sinωt = 2cosθsinωt

In this way, two AC output signals "2 sin θ sin ωt" and "2 cos θ si" respectively amplitude-modulated by the two periodic amplitude functions (sin θ and cos θ) including the angle variable θ correlated with the rotational position to be detected.
nωt ”is obtained (hereinafter, the coefficient“ 2 ”is omitted). This is equivalent to the sine phase output signal sin θ sin ωt and the cosine phase output signal cos θ sin ωt of the detector conventionally known as a resolver. It should be noted that the names of sine phase and cosine phase, and the sine of the amplitude function of the two AC output signals, and the way of expressing the cosine are for convenience, as long as one is the sine and the other is the cosine, which one You can say that. That is, Va−Vc = cos θ sin ωt, and Vb−V
It may be expressed that d = sin θ sin ωt.

Here, the compensation of the temperature drift characteristic will be described. The impedances of the coils L1 to L4 change according to the temperature, and the output voltages Va to Vd also change. However, AC output signals sin θ sin ωt and cos of sine and cosine function characteristics obtained by arithmetically combining these
At θ sin ωt, “Va−Vc” and “Vb−
Since the temperature drift error of the coil is completely compensated by the calculation of “Vd”, it is not affected by the coil impedance change due to the temperature drift. Therefore, accurate detection is possible.

In this embodiment, the rotational position can be detected by either the phase detection method or the voltage detection method based on the two AC output signals sin θ sin ωt and cos θ sin ωt output from the arithmetic units 31 and 32.
The phase detection method in this case may be configured using, for example, the technique disclosed in Japanese Patent Application Laid-Open No. 9-126809 filed by the present applicant. For example, one AC output signal sin θ sin ωt is electrically shifted by 90 degrees in the shift circuit 33 to generate an AC signal sin θ cos ωt, and the other AC output signal cos θ sin ωt is added and synthesized by the adder 34 and the subtractor 35. And sin (ωt + θ) and sin (ωt−θ), which are phase-shifted in the advance and retard directions depending on θ (since the phase component θ is converted to an AC phase shift). Signal). Then, the comparator 36.37 detects the zero-cross of the phase-shifted AC signals sin (ωt + θ) and sin (ωt−θ), and the zero-cross detection pulse Lp of the phase detection AC signal sin (ωt + θ).
And a zero-crossing detection pulse Lm of the delayed detection AC signal sin (ωt−θ), and the digital processing device 4
Enter 0. The digital processing device 40 digitally detects the phase shift amount + θ of the advance phase by measuring the time difference from the zero phase time point of the reference signal sinωt to the generation time point of the zero phase detection pulse Lp of the advance phase, and the reference signal si.
By measuring the time difference from the zero phase time point of nωt to the generation time point of the delayed zero cross detection pulse Lm, the phase shift amount −θ of the delayed phase is digitally detected. The error ± δ due to the temperature drift and other error factors is included in the phase shift amount + θ of the advance phase and the phase shift amount −θ of the delay phase in the same direction and the same amount. Therefore, in the digital processing device 40, By performing a predetermined calculation including addition or subtraction of the phase detection values + θ and −θ of the advanced phase and the delayed phase, it is possible to obtain accurate phase detection data θ with the error ± δ removed. As the digital processing device 40, for example, a general-purpose microcomputer can be used. By the compensation calculation using the phase detection values + θ and −θ of the advanced phase and the delayed phase, it is possible to completely remove the temperature drift error component that could not be removed by differentially calculating the outputs of the coils. . Further, since the phase shift amount θ is digitally measured, the absolute rotational position can be detected with high detection resolution. Of course, not only digital detection but also analog detection is possible. The whole or part of the detection circuit as shown in FIG. 2 may be incorporated and arranged in the casing of the stator section 1 shown in FIG. Alternatively, all or part of the detection circuit may be arranged at a position appropriately separated from the stator unit 1 and connected by necessary wiring.

FIG. 3 shows a second embodiment of the present invention, wherein (a) is a schematic sectional view in the axial direction and (b) is a schematic front view. In FIG. 3, the bearing 20 is a retainer (not shown).
A plurality (7 in the illustrated example) held at a predetermined interval by
Ball (rolling elements) 11 and 14 are arranged between the inner ring 12 and the outer ring 13 to form a rolling bearing. Similarly to the above, the retainer is not shown for the sake of convenience, but the retainer itself may be appropriately used for an existing bearing (ball bearing). In the illustrated example, the target shaft 5 that bears
0 is connected to the inner ring 12, and the inner ring 1 is rotated as the shaft 50 rotates.
2 rotates. The outer ring 13 is fixed to a machine frame or the like and stands still. In the bearing 20 of FIG. 3, a plurality of (7 in the illustrated example) balls are composed of a first group of balls 11 made of a magnetically responsive material (for example, a steel ball) and a material that does not respond to magnetism (for example, a ceramic). A second group of balls 14 The balls 11 of the first group and the balls 14 of the second group are continuously arranged, and each group is composed of approximately the same number of balls, and two groups divide one circle into two. In the illustrated example, since the number of balls is an odd number (7), the first group of balls 11 (shown with diagonal lines) is four, and the second group of balls 14 is three. Thus, the first group of balls 11
Constitutes an aggregate of magnetically responsive substances which covers a circumferential range of about 180 degrees as a whole. In addition, the balls 14 of the second group constitute an aggregate of magnetic non-responsive substances that cover the circumferential range of approximately 180 degrees as a whole.

Also in the example of FIG. 3, the stator portion 2 is fixed to the outer ring 13 and stands still. This stator portion 2 also has a plurality of AC excitation magnetic poles A, B, C, D at predetermined intervals along the circumference formed by the rolling trajectories of the balls 11, 14 held by the retainer (that is, the rotational trajectory of the retainer). It will be arranged. However, in the example of FIG. 3, as shown in (b),
Each of the AC excitation magnetic poles A, B, C, D is wide so as to cover a width of about 90 degrees or less of the circumference. That is, the magnetic cores 2a, 2b, 2c, 2d of the AC excitation magnetic poles A, B, C, D in FIG. 3 are wide, and the coils L1, L2, L3, L4 are wound around the magnetic cores. It has been turned. Similarly to the above, the coils L1 to L4 are excited by a predetermined AC signal (for example, sinωt). The arrangement of the wide AC exciting magnetic poles A, B, C, and D is such that when the balls 11 and 14 of the first and second groups held by the retainer make one revolution around the shaft circumference, impedance changes of one cycle It is set to occur at poles AD.

In the same manner as described above, the voltages Va, Vb, Vc and Vd generated in the coils L1 to L4 of the poles A to D are
The respective amplitudes are sine function (sin θ), cosine function (cos θ), and minus sine function (−sin).
θ) and a minus cosine function (−cos θ). However, in this second embodiment,
Phase angle θ of impedance change of each pole A to D is 0 to 3
The mechanical displacement, which indicates a change of 60 degrees in one cycle, corresponds to the retainer, that is, the balls 11 and 14 making one revolution around the shaft circumference. Similarly to the above, the rotation of the retainer with respect to the rotation of the target shaft 50, that is, the rolling of the balls 11 and 14 is decelerated in the opposite direction. Therefore, θ does not directly indicate the rotation angle of the target shaft 50, but θ corresponds to the rotation position of the target shaft 50 in a predetermined relationship, and the rotation of the target shaft 50 is measured by measuring θ. The position can be detected.

4A and 4B show a third embodiment of the present invention, wherein FIG. 4A is a schematic sectional view in the axial direction, and FIG. 4B is a schematic front view. In FIG. 4, the bearing 10 includes a plurality of balls (rolling elements) (seven in the illustrated example) held at predetermined intervals by a retainer (not shown), as in the case shown in FIG. 1 or 3. A rolling type bearing 14 is arranged between the inner ring 12 and the outer ring 13. However, in the third embodiment, the magnetic property of the ball 14 is not particularly limited, but a magnetic non-responsive member such as ceramic is preferable. Also in the example of FIG. 4, the stator part 3 is fixed to the outer ring 13 and stands still. The stator portion 3 is formed by arranging a plurality of AC excitation magnetic poles A, B, C and D along the circumference of the outer ring 13 at predetermined intervals (for example, 90 degree intervals). Each pole A to D is composed of magnetic cores 3a, 3b, 3c, 3d and coils L1, L2, L3, L4 wound around them. Magnetic core 3
The ends of a, 3b, 3c and 3d are oriented inward in the axial direction. That is, in the case of FIG. 4, unlike in FIGS. 1 and 3, the direction of the magnetic flux by the AC excitation magnetic poles A to D is the radial direction. A magnetically responsive cam portion 5 made of a magnetically responsive member such as a magnetic material or a conductor is provided so as to face the AC excitation magnetic poles A to D of the stator portion 3. The magnetically responsive cam portion 5 is fixed to the inner ring 12 and rotates together with the inner ring 12 as the target shaft 50 rotates. Magnetically responsive cam part 5
Has a cam shape that is eccentric with respect to the circumference around the target shaft 50. The shape.

Similarly to the above, each of the coils L1 to L4 is excited by a predetermined AC signal (for example, sinωt). The relationship between the arrangement of the AC excitation magnetic poles A to D on the stator part 3 side and the cam shape of the magnetically responsive material of the magnetically responsive cam part 5 on the inner ring 12 side is, for example, one cycle when the inner ring 12 makes one rotation. It is set so that the impedance change of 1 occurs at each pole A to D. Further, similarly to the above, the voltages Va, Vb, Vc and Vd generated in the coils L1 to L4 of the poles A to D are
The respective amplitudes are sine function (sin θ), cosine function (cos θ), and minus sine function (−sin).
θ) and a minus cosine function (−cos θ). However, in the third embodiment, the mechanical displacement indicating the phase change θ of the impedance change of each pole A to D in one cycle of 0 ° to 360 ° is that the inner ring 12, that is, the target shaft 50 makes one rotation. It corresponds to. Therefore, in this third embodiment, θ is the target axis 50.
The rotation position of the target shaft 50 can be detected by measuring this θ.

FIG. 5 shows a fourth embodiment of the present invention. (A) is a schematic axial cross-sectional view and (b) is a schematic front view. In FIG. 5, the bearing 10 includes a plurality of balls (rolling elements) 14 (seven in the illustrated example) 14 held at predetermined intervals by a retainer 15 as in the case of FIG. 1 or 3.
Is a rolling type bearing in which is disposed between the inner ring 12 and the outer ring 13. However, in the fourth embodiment, the balls 14 are preferably made of a magnetic non-responsive material such as ceramic. Also in the example of FIG.
Fixed against and stationary. The stator portion 4 has a plurality of alternating-current excitation magnetic poles A, B, C, and D arranged at predetermined intervals (for example, 90 ° intervals) along the circumference formed by the movement trajectory of the retainer 15. The poles A to D are magnetic cores 4a, 4b, 4
c, 4d and coils L1, L2, L3 wound around them
And L4. Magnetic cores 4a, 4b, 4c, 4
The end of d faces the retainer 15 in the axial direction. That is, in the case of FIG. 5, as in FIGS. 1 and 3, the direction of the magnetic flux due to the AC excitation magnetic poles A to D is the axial direction. Stator part 4
Magnetic response made of a magnetically responsive member such as a magnetic material or a conductor having a cam shape along the circumference of the retainer 15 so as to face the AC excitation magnetic poles A to D and having a bias with respect to the circumference. The sex cam portion 15a is provided. The magnetically responsive cam portion 15a is, for example, as shown in FIG.
It is an eccentric cam shape that exhibits one cycle of eccentricity characteristics for one rotation of the retainer 15.

Similarly to the above, each of the coils L1 to L4 is excited by a predetermined AC signal (for example, sinωt). Arrangement of the AC excitation magnetic poles A to D on the side of the stator 4 and the retainer 15
As shown in FIG. 5B, the relationship between the magnetic responsive cam portion 15a on the side and the cam shape of the magnetic responsive material is, for example, as shown in FIG. ~ D are set to occur. Further, similarly to the above, each coil L1 to each pole A to D is
The voltages Va, Vb, Vc, and Vd generated in L4 are such that their amplitudes show characteristics of a sine function (sin θ), a cosine function (cos θ), a negative sine function (−sin θ), and a negative cosine function (−cos θ), respectively. Is set to. However, in the fourth embodiment, the phase angle θ of the impedance change of each pole A to D is 0 degrees to 360 degrees.
The mechanical displacement, which shows a change of one cycle of the
Corresponds to rotating the shaft circumference once. Similarly to the above, the rotation of the retainer 15 is decelerated in the opposite direction with respect to the rotation of the target shaft 50. Therefore, θ does not directly indicate the rotation angle of the target shaft 50, but θ corresponds to the rotation position of the target shaft 50 in a predetermined relationship, and the rotation of the target shaft 50 is measured by measuring θ. The position can be detected. For example, when the reduction ratio between the target shaft 50 and the retainer 15 is 9: 1, the absolute rotational position of the target shaft 50 over 9 rotations can be detected by detecting the absolute rotation angle θ of the retainer 15 over one rotation.

FIG. 5C shows a modification of the magnetically responsive cam portion 15b provided on the retainer 15. The magnetically responsive cam portion 15b has an elliptical cam shape,
Two cycles of impedance change for each pole A
~ D are set to occur. Also in this case, the detectable θ does not directly indicate the rotation angle of the target shaft 50, but it corresponds to the rotational position of the target shaft 50 in a predetermined relationship, and by measuring this θ. The rotational position of the target shaft 50 can be detected. For example, when the reduction ratio between the target shaft 50 and the retainer 15 is 9: 1, the absolute rotational position of the target shaft 50 over four and a half rotations can be detected by detecting the absolute rotation angle θ over the half rotation of the retainer 15.
For example, since the rotatable range of the steering wheel of an automobile is about four and a half to five rotations, the present invention is applied to a bearing portion for bearing the steering wheel, and the target shaft 50
If the reduction ratio between the retainer 15 and the retainer 15 is designed to be 9: 1 or about 10: 1, it is possible to easily and absolutely detect the rotational position of the entire steering wheel rotatable range of about 4 1/2 to 5 rotations. Become.

The fifth embodiment of the present invention can be constructed by combining the embodiment shown in FIG. 4 and the embodiment shown in FIG. That is, in the rotational position detecting device according to the fifth embodiment, in the rolling type bearing 10 in which the plurality of rolling elements (balls 14) held by the retainer 15 are arranged between the inner ring 12 and the outer ring 13. A first stator portion 3 (Fig. 4) fixed to the outer ring 13 and having a plurality of AC excitation magnetic poles arranged at predetermined intervals along the circumference thereof,
It is provided with a first detection unit that is fixed to the inner ring 12 and is composed of a first magnetically responsive cam unit 5 (FIG. 4) having a cam shape that is biased with respect to the circumference thereof. The second stator portion 4 (FIG. 5) fixed to the second stator portion 4 (FIG. 5), in which a plurality of AC excitation magnetic poles are arranged at predetermined intervals along the circumference formed by the movement locus of the retainer 15, and the second stator portion 4 arranged on the retainer 15.
It has a second detection part composed of the magnetically responsive cam part 15a or 15b (FIG. 5). Accordingly, the first detection unit (FIG. 5) can detect the rotational position of the target shaft 50 within one rotation by absolute, and the second detection unit can detect the rotational position of the target shaft 50 over multiple rotations by absolute. It is possible to detect the rotational position over multiple rotations with high resolution and absolute by the combination of both.

In each of the above embodiments, in the bearing,
The inner ring 12 is moving and the outer ring 13 is stationary, but the reverse is also possible. In that case, it goes without saying that the stator parts 1, 2, 3, 4 are fixed to the stationary inner ring 12. Further, the magnetically responsive material is not limited to a magnetic body, and a good conductor such as copper may be used, or a hybrid structure of a magnetic body and a good conductor may be used. The rolling elements of the bearing are not limited to balls and may be rollers. The coil structure for detection is not limited to the type for detecting the impedance of the exciting coil as in the above embodiment, but a primary coil and a secondary coil may be provided in a pair so that the induction output is taken out from the secondary coil. Good. Further, the AC excitation method is not limited to the type in which one-phase excitation is performed with sin ωt as in the above embodiment, but sin ωt
It is also possible to use a type in which two-phase excitation is performed by using the cos and t. The number of AC excitation magnetic poles is not limited to 4 poles as in the above-mentioned embodiment, but may be 2 poles (sine and cosine), 3 poles, 6 poles,
It may have eight poles or the like.

[0029]

As described above, according to the present invention, by adopting the structure for detecting the displacement of the rolling element of the bearing, the rotational position detecting device having a simple structure can be obtained, and the manufacturing cost is low. I'm done. Further, since the rotational position is detected based on the output signal indicating the impedance change corresponding to the position change of the rolling element, the absolute position can be detected with high detection resolution. Further, by detecting the relative rotational position of the outer ring and the inner ring by the combination of the stator part and the magnetically responsive cam part provided on the outer ring and the inner ring, respectively, it is possible to detect the rotational position of the bearing target shaft. In this case as well, in this case, the structure is simple and the manufacturing cost is low. Further, by forming a cam-shaped magnetically responsive cam portion showing a deviation with respect to the circumference formed by the movement locus of the retainer, and detecting rotation of the magnetically responsive cam portion provided in the retainer by the stator portion, A position detection device having a simple structure can be provided.

[Brief description of drawings]

FIG. 1 is a schematic axial sectional view and a schematic front view showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a detection circuit applicable to each embodiment of the present invention.

FIG. 3 is a schematic axial sectional view and a schematic front view showing a second embodiment of the present invention.

FIG. 4 is a schematic axial sectional view and a schematic front view showing a third embodiment of the present invention.

FIG. 5 is a schematic axial sectional view and a schematic front view showing a fourth embodiment of the present invention.

[Explanation of symbols]

1, 2, 3, 4 Stator parts A, B, C, D AC excitation magnetic poles L1, L2, L3, L4 Coils 1a to 1d, 2a to 2d, 3a to 3d, 4a to 4d Magnetic cores 10, 20 Bearings 11 Ball (Magnetic response) 14 Ball (Magnetic non-responsiveness) 12 Inner ring 13 Outer ring 15 Retainers 5, 15a, 15b Magnetically responsive cam unit 50 Bearing target shaft

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F077 AA25 AA27 CC02 NN07 NN08                       TT08 TT44 TT85 VV02 VV13                 3J101 AA03 AA32 AA42 AA62 BA10                       BA53 BA54 BA56 BA70 EA74                       FA44 FA55 FA60

Claims (5)

[Claims] 1. A rolling type bearing comprising a plurality of rolling elements held by a retainer at predetermined intervals between an inner ring and an outer ring, wherein a rolling locus of the rolling element held by the retainer is The rolling element comprises a magnetically responsive material, and a plurality of alternating-current excitation magnetic poles are arranged at predetermined intervals along the circumference of the rolling element. The rolling element is rolled along with the retainer together with the retainer. With this, the position of the rolling element with respect to each of the AC excitation magnetic poles changes, and an output signal indicating an impedance change corresponding to the position change is taken out by a coil arranged in the AC excitation magnetic pole. Rotational position detector. 2. A rolling type bearing comprising a plurality of rolling elements held by a retainer at predetermined intervals between an inner ring and an outer ring, wherein the rolling locus of the rolling element held by the retainer is The stator includes a plurality of alternating-current excitation magnetic poles arranged at predetermined intervals along the circumference, and the plurality of rolling elements are composed of a first group of magnetically responsive materials and a material that does not respond to magnetism. A first group of rolling elements for each of the alternating magnetic excitation poles as the rolling element rolls along the circumference together with the retainer.
And a rotational position detecting device for a bearing, wherein the position of the second group changes and an output signal showing an impedance change corresponding to the position change is taken out by a coil arranged in the AC excitation magnetic pole. 3. A bearing comprising a plurality of rolling elements arranged between an inner ring and an outer ring, wherein the bearing is fixed to one of the outer ring and the inner ring, and a plurality of AC excitations are provided at predetermined intervals along the circumference thereof. A magnetically responsive cam portion fixed to the other of the outer ring or the inner ring and having a cam shape that is biased with respect to the circumference of the outer ring or the inner ring. With relative rotation,
Rotational position detection in a bearing characterized in that the position of the magnetically responsive cam portion with respect to each of the AC excitation magnetic poles changes, and an output signal showing an impedance change corresponding to this position change is taken out by a coil arranged in the AC excitation magnetic poles. apparatus. 4. A rolling type bearing comprising a plurality of rolling elements held by a retainer arranged between an inner ring and an outer ring, wherein a plurality of rolling elements are provided at predetermined intervals along a circumference formed by a moving path of the retainer. The retainer is provided with a stator portion in which an AC excitation magnetic pole is disposed, and the retainer is formed with a cam-shaped magnetically responsive cam portion showing a deviation with respect to a circumference formed by a movement locus of the retainer. With the movement along the circumference, the position of the magnetically responsive cam portion changes with respect to each of the AC exciting magnetic poles, and an output signal showing an impedance change corresponding to this position change is taken out by a coil arranged in the AC exciting magnetic pole. A rotational position detecting device for a bearing, which is characterized in that 5. A rolling type bearing comprising a plurality of rolling elements held by a retainer arranged between an inner ring and an outer ring, wherein the rolling bearing is fixed to one of the outer ring and the inner ring and extends along the circumference thereof. A first arrangement comprising a plurality of alternating-current excitation magnetic poles arranged at predetermined intervals
A first cam-shaped member fixed to the stator part and the other of the outer ring and the inner ring and having a cam shape that is biased with respect to the circumference thereof.
A first detection unit including a magnetically responsive cam unit,
With the relative rotation of the inner ring with respect to the outer ring, the position of the first magnetically responsive cam portion with respect to each AC excitation magnetic pole of the first stator portion changes, and an output signal indicating an impedance change corresponding to the position change is output. A second stator portion, in which a plurality of AC excitation magnetic poles are arranged at predetermined intervals along the circumference of the retainer movement locus, and the retainer, and the retainer. A second magnetically responsive cam portion disposed in the second detecting portion, wherein the retainer moves along the circumference as the retainer moves along the circumference. The position of the second magnetically responsive cam portion changes, and an output signal indicating an impedance change corresponding to this change in position is extracted by a coil arranged on the AC excitation magnetic pole of the second stator portion. Rotational position detection device for bearings.